This invention relates to a stud arrangement through which the housing of a servomotor is connected to a master cylinder.
When the movable wall in servomotors were suspended in air such as illustrated in U.S. Pat. No. 3,110,031, bolts were adequate to attach a master cylinder to the housing of the servomotor.
Later it was discovered that the operational characteristics of a servomotor could be enhanced if the movable wall were suspended in vacuum as illustrated by the servomotor shown in U.S. Pat. No. 3,292,502. In order to assure that the openings in such a servomotor were closed, seals were required on the input and output push rods. In addition, the mounting studs were welded to housing of the servomotor. Unfortunately, welding can change the molecular structure of the housing in such a manner that a vacuum leak may occur through the openings in the housing for the studs. For example, in a servomotor master cylinder combination such as shown in U.S. Pat. No. 4,022,081 because of the cantilever length between the fire wall studs and the end of the master cylinder, the flexing force induced into the shell under certain conditions may cause the weld to crack. When a weld cracks, a vacuum leak path can be produced and as a result the operation of the servomotor rendered inadequate to provide an input force to effect a brake application.
In order to reduce the stress placed on the weld, it was suggested that the housing of the servomotor be strengthened and the physical size of the stud head be increased to spread the forces over a larger area. However with an increasing effort to remove weight from the components in a vehicle such a solution has generally been unacceptable.